The Felsa 4031 watch movement, introduced in 1977, is a landmark in automatic watch design with its thinness and inclusion of date and sweep second features. It incorporates a micrometer regulator and two serially coupled barrels, one with a fixed spring and one with a slip spring. The Felsa 4031 movement is equivalent to the Lemania 8810 movement. In terms of functions, it includes an automatic winding mechanism, a quickset date feature, and a hack feature. This mechanical movement does not feature a second hand and has been in use since 1977.